System and method for providing a self heating adjustable TiSi2 resistor

ABSTRACT

A system and method is disclosed for providing a self heating adjustable titanium disilicon (TiSi 2 ) resistor. A triangularly shaped layer of polysilicon is placed a layer of insulation material. A layer of titanium is applied over the polysilicon and heated to form a layer of C49 type of TiSi 2 . A current is then applied to the small end of the triangularly shaped layer of C49 TiSi 2 . The current generates heat in a high resistance portion of the triangularly shaped layer of C49 TiSi 2  and converts a portion of the C49 TiSi 2  to C54 TiSi 2 . The lower resistance of the C54 TiSi 2  decreases the effective resistance of the resistor. A desired value of resistance may be selected by adjusting the magnitude of the applied current.

This application is a divisional of prior U.S. patent application Ser.No. 10/801,268 filed on Mar. 16, 2004 now U.S. Pat. No. 7,166,518.

TECHNICAL FIELD OF THE INVENTION

The present invention is generally directed to manufacturing technologyfor semiconductor devices and, in particular, to a system and method forproviding a self heating adjustable titanium disilicon (TiSi₂) resistor.

BACKGROUND OF THE INVENTION

Prior art resistors for semiconductor devices are typically constructedso that the resistance of a resistor is a fixed value. The fixed valueof resistance is dependent upon the circuit parameters selected tomanufacture the resistor.

There are some circuit applications in which it would be desirable tohave a resistor that could have the value of the resistance adjustedafter the wafer fabrication is complete and the device is packaged.Prior art resistors for semiconductor devices are not generally designedto provide an adjustable value of resistance.

Therefore, there is a need in the art for a system and method forproviding a resistor that is capable of having the resistance valueadjusted after packaging. That is, there is a need in the art for asystem and method for providing a resistor that is capable of having oneof a plurality of possible resistances.

SUMMARY OF THE INVENTION

To address the above-discussed deficiencies of the prior art, it is aprimary object of the present invention to provide a system and methodfor providing a resistor that is capable of having the resistanceadjusted after the unit is packaged.

In one advantageous embodiment of the present invention an adjustabletitanium disilicon (TiSi₂) resistor is constructed in the followingmanner. A triangularly shaped layer of polysilicon is placed on aninsulated layer such as silicon dioxide mounted on a handle wafer. Thena layer of titanium is applied over the triangularly shaped layer ofpolysilicon. Then the layer of titanium is heated to a temperature ofapproximately six hundred twenty degrees Centigrade (620° C.) to form atriangularly shaped layer of C49 type titanium disilicon (TiSi₂) in thepolysilicon layer. The unconverted titanium is then removed.

Then a dielectric layer is placed over the triangularly shaped TiSi₂layer. A mask and etch procedure is performed to etch the dielectriclayer to form a contact receptacle trench for receiving an input contactat the small end of the triangularly shaped TiSi₂ layer and a contactreceptacle trench for receiving an output contact at the large end ofthe triangularly shaped TiSi₂ layer. A metal deposition procedure and ametal etch procedure are performed to form the input contact and theoutput contact. An additional mask and metal deposition procedure isperformed to form an input metal connector for the input contact and anoutput metal connector for the output contact.

A current is provided to the triangularly shaped TiSi₂ layer through theinput contact that is coupled to the small end of the triangularlyshaped TiSi₂ layer. The current self heats the narrowest part of the C49TiSi₂ resistor due to the high power density portion of the triangularlyshaped TiSi₂ layer and converts a portion of the C49 type TiSi₂ to C54type TiSi₂. The C54 type TiSi₂ has a lower resistance than the C49 typeTiSi₂. The lower resistance of the C54 type TiSi₂ decreases theeffective resistance of this portion of the triangularly shaped TiSi₂layer and decreases the power density, allowing the converted area tocool. Now the total resistance of the triangularly shaped resistor hasbeen permanently decreased due to the change bulk resistivity of thesmall area converted to C54 type TiSi₂.

As the magnitude of the current is increased the power density in thenext narrowest part of the triangle will reach a point where selfheating converts more of the C49 type TiSi₂ to the C54 type TiSi₂thereby further reducing the effective resistance of the resistor anddropping the power density and allowing the section to cool as before.

A desired value of resistance for the adjustable resistor may beselected by setting the magnitude of the current to a value thatproduces a desired value of resistance up to the point where the entiretriangle has been converted to C54 type TiSi₂ and so reaches the lowestvalue of resistance. It is necessary that the resistance of thenarrowest part of the triangle, when converted to C54 type TiSi₂, have alower resistance than the widest part of the triangle while it is C49type TiSi₂. Because the difference in bulk resistivity is about 14.5micro-ohm-cm to 70.0 micro-ohm-cm, a difference in width of about four(4) to one (1) is appropriate.

It is an object of the present invention to provide a system and methodfor providing a resistor that is capable of having more than one valueof resistance.

It is also an object of the present invention to provide a system andmethod for providing a self heating adjustable TiSi₂ resistor.

It is yet another object of the present invention to provide a systemand method for providing an adjustable resistor in which a desired valueof resistance may be selected by setting a magnitude of a current to avalue that produces a desired value of resistance.

It is still another object of the present invention to provide a systemand method for providing a self heating adjustable TiSi₂ resistor inwhich a current is capable of generating heat in an area of high powerdensity and converting a portion of C49 type TiSi₂ to C54 type TiSi₂ todecrease the effective resistance of the resistor.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention so that those skilled in the art maybetter understand the detailed description of the invention thatfollows. Additional features and advantages of the invention will bedescribed hereinafter that form the subject of the claims of theinvention. Those skilled in the art should appreciate that they mayreadily use the conception and the specific embodiment disclosed as abasis for modifying or designing other structures for carrying out thesame purposes of the present invention. Those skilled in the art shouldalso realize that such equivalent constructions do not depart from thespirit and scope of the invention in its broadest form.

Before undertaking the Detailed Description of the Invention below, itmay be advantageous to set forth definitions of certain words andphrases used throughout this patent document: the terms “include” and“comprise,” as well as derivatives thereof, mean inclusion withoutlimitation; the term “or,” is inclusive, meaning and/or; the phrases“associated with” and “associated therewith,” as well as derivativesthereof, may mean to include, be included within, interconnect with,contain, be contained within, connect to or with, couple to or with, becommunicable with, cooperate with, interleave, juxtapose, be proximateto, be bound to or with, have, have a property of, or the like; and theterm “controller” means any device, system or part thereof that controlsat least one operation, such a device may be implemented in hardware,firmware or software, or some combination of at least two of the same.It should be noted that the functionality associated with any particularcontroller may be centralized or distributed, whether locally orremotely. Definitions for certain words and phrases are providedthroughout this patent document, those of ordinary skill in the artshould understand that in many, if not most instances, such definitionsapply to prior uses, as well as future uses, of such defined words andphrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates a prior art graph of resistance versus temperatureshowing the resistance of a combination of titanium (Ti) and silicon(Si) as a function of temperature;

FIG. 2 illustrates a top plan view of an advantageous embodiment of atriangularly shaped self heating adjustable TiSi₂ resistor of thepresent invention;

FIG. 3 illustrates a perspective side view of the resistor shown in FIG.2;

FIGS. 4 through 11 illustrate successive stages in the construction ofan advantageous embodiment of a self heating adjustable TiSi₂ resistorin accordance with the principles of the present invention;

FIG. 12 illustrates the operation of an advantageous embodiment of aself heating adjustable TiSi₂ resistor of the present invention at afirst value of current I₁;

FIG. 13 illustrates the operation of an advantageous embodiment a selfheating adjustable TiSi₂ resistor of the present invention at a secondvalue of current I₂;

FIG. 14 illustrates a flow chart showing the steps of a first portion ofan advantageous embodiment of the method of the present invention; and

FIG. 15 illustrates a flow chart showing the steps of a second portionof an advantageous embodiment of the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 through 15, discussed below, and the various embodiments used todescribe the principles of the present invention in this patent documentare by way of illustration only and should not be construed in any wayto limit the scope of the invention. Those skilled in the art willunderstand that the principles of the present invention may beimplemented in any type of suitably arranged resistor.

FIG. 1 illustrates a prior art graph of resistance versus silicidationtemperature showing the resistance of a titanium (Ti) and silicon (Si)combination as a function of silicidation temperature. The measure ofresistance is ohms per unit area. The resistance scale runs from ten(10) ohms per unit area to one hundred ten (110) ohms per unit area. Themeasure of temperature is degrees Centigrade. The temperature scale runsfrom zero degrees Centigrade (0° C.) to one thousand degrees Centigrade(1000° C.).

At the lower temperatures the resistance of the combination of thetitanium (Ti) and the silicon (Si) increases approximately linearly withincreasing temperature. The maximum resistance of approximately ninetysix (96) ohms per unit area is reached when the temperature isapproximately six hundred degrees Centigrade (600° C.). In thetemperature range of approximately six hundred degrees Centigrade (600°C.) to six hundred fifty degrees Centigrade (650° C.) the titanium andthe silicon form the C49 type of titanium disilicon (TiSi₂). As shown inFIG. 1, the resistance of the C49 type TiSi₂ continues to drop as thetemperature increases.

When the temperature increases above approximately seven hundred degreesCentigrade (700° C.) the titanium and the silicon form the C54 type oftitanium disilicon (TiSi₂) As also shown in FIG. 1, the resistance ofthe C54 type TiSi₂ continues to drop as the temperature increases.Therefore the resistance of the C54 type TiSi₂ is lower than theresistance of the C49 type TiSi₂. The resistor of the present inventionmakes use of the thermal properties of TiSi₂ to adjust the value ofresistance in the resistor.

FIG. 2 illustrates a top plan view of an advantageous embodiment of atriangularly shaped self heating adjustable TiSi₂ resistor 200 of thepresent invention. Resistor 200 comprises a resistor layer 210 that isformed having a triangular shape. As will be more fully described,resistor layer 210 comprises a layer of polysilicon over which atitanium layer has been applied. The titanium layer is heated to atemperature of approximately six hundred twenty degrees Centigrade (620°C.) to form C49 type TiSi₂ in resistor layer 210.

The small end of the triangle of resistor layer 210 is electricallycoupled to input contact 220. The large end of the triangle of resistorlayer 210 is electrically coupled to output contact 230. An input metalconnector 240 is electrically coupled to input contact 220 and an outputmetal connector 250 is electrically coupled to output contact 230.Current from metal connector 240 is supplied to resistor layer 210through input contact 220. The current then flows through resistor layer210 to output contact 230. The current exits output contact 230 throughoutput metal connector 250.

FIG. 3 illustrates a perspective side view of the resistor 200 shown inFIG. 2. The resistor layer 210, input contact 220, output contact 230,input metal connector 240, and output metal connector 250 are allmounted on an underlying insulating layer such as silicon dioxide (notshown in FIG. 3).

FIGS. 4 through 11 illustrate successive stages in the construction ofan advantageous embodiment of a self heating adjustable TiSi₂ resistor200 in accordance with the principles of the present invention. Tosimplify the drawings the reference numerals from previous drawings willsometimes not be repeated for structures that have already beenidentified.

First, an insulating layer such as silicon dioxide 420 is mounted on ahandle wafer 410. Then a triangularly shaped polysilicon layer 430 isplaced on the insulating layer 420. The result of these steps is shownin FIG. 4.

Then a layer of titanium is applied over the triangularly shaped layerof polysilicon 430. In one advantageous embodiment the thickness of thetitanium layer is approximately five hundred Angstroms (500 Å). Thetitanium layer is then heated to a temperature of approximately sixhundred twenty degrees Centigrade (620° C.) to form C49 type TiSi₂ inpolysilicon layer 430. After the heating process is completed, anyremaining unconverted titanium is then stripped away from polysiliconlayer 430 leaving only C49 type TiSi2 in TiSi₂ layer 510. The result ofthese procedures is shown in FIG. 5.

A dielectric layer 610 is then deposited over the TiSi2 layer 510 andportions of the silicon dioxide layer 420. The result of the dielectricdeposition step is shown in FIG. 6. A mask and etch procedure is thenperformed on dielectric layer 610 to etch contact receptacle trenches620 in dielectric layer 610. The result of the mask and etch procedureis shown in FIG. 7.

Then a metal deposition procedure is employed to deposit metal 810 intothe contact receptacle trenches 620 to form input contact 220 and outputcontact 230. The result of the metal deposition procedure is shown inFIG. 8. Then a metal etch procedure is performed to etch away excessmetal 810 and the remaining portions of dielectric layer 610. The resultof the etch procedure is shown in FIG. 9.

Then a mask 1010 is placed over the TiSi₂ layer 510 and the inputcontact 220 and the output contact 230. A metal deposition procedure isthen performed to form the input metal connector 240 and the outputmetal connector 250. The result of these steps is shown in FIG. 10. Thenthe mask 1010 is stripped away and resistor 200 has the structure shownin FIG. 11.

FIG. 12 illustrates the operation of an advantageous embodiment of aself heating adjustable TiSi₂ resistor 200 of the present invention at afirst value of current I₁. The current I₁ passes through input metalconnector 240 to input contact 220 and then into resistor layer 210.Resistor layer 210 comprises TiSi₂ layer 510 and polysilicon layer 430.The current I₁ passes out of resistor layer 210 through output contact230 and output metal connector 250.

The narrow end of resistor layer 210 will have a higher power densitythan the wide end of resistor layer 210. That is, the portions ofresistor layer 210 that are nearest to input contact 220 will experiencea higher power density than those portions of resistor layer 210 thatare farther from input contact 220.

The portion 1210 of resistor layer 210 in FIG. 12 represents an area ofhigh power density for current I₁. The high power density in portion1210 generates heat. When the temperature in portion 1210 exceedsapproximately seven hundred degrees Centigrade (700° C.), then the C49type TiSi₂ within portion 1210 is converted to C54 type TiSi₂. Becausethe resistance of C54 type TiSi₂ is less than the resistance of C49 typeTiSi₂ the resulting effective resistance of resistor layer 210 decreasesafter the C49 type TiSi₂ within portion 1210 has been converted to C54type TiSi₂. The conversion of the C49 type TiSi₂ to the C54 type TiSi₂is initiated by the “self heating” that is created by the high powerdensity within portion 1210 of resistor layer 210.

After the portion 1210 has been converted to C54 type TiSi₂ theresistance of resistor layer 210 drops so that, for a given value ofcurrent I₁, no more of the C49 type TiSi₂ will be converted. This meansthat the reaction is self limiting.

FIG. 13 illustrates the operation of an advantageous embodiment a selfheating adjustable TiSi₂ resistor 200 of the present invention at asecond value of current I₂. As in the case for the first value ofcurrent I₁ shown in FIG. 12, the current I₂ in FIG. 13 passes throughinput metal connector 240 to input contact 220 and then into resistorlayer 210. Resistor layer 210 comprises TiSi₂ layer 510 and polysiliconlayer 430. The current I₂ passes out of resistor layer 210 throughoutput contact 230 and output metal connector 250.

Also as in the case for the current I₁, the narrow end of resistor layer210 will have a higher power density than the wide end of resistor layer210. That is, the portions of resistor layer 210 that are nearest toinput contact 220 will experience a higher power density than thoseportions of resistor layer 210 that are farther from input contact 220.

The portion 1310 of resistor layer 210 in FIG. 13 represents an area ofhigh power density for current I₂. Because the current I₂ is greater inmagnitude than the current I₁, the area of portion 1310 is greater thanthe area of portion 1210. As in the case of portion 1210, the high powerdensity in portion 1310 generates heat. When the temperature in portion1310 exceeds approximately seven hundred degrees Centigrade (700° C.),then the C49 type TiSi₂ within portion 1310 is converted to C54 typeTiSi₂. Because the resistance of C54 type TiSi₂ is less than theresistance of C49 type TiSi₂ the resulting effective resistance ofresistor layer 210 decreases after the C49 type TiSi₂ within portion1310 has been converted to C54 type TiSi₂. The conversion of the C49type TiSi₂ to the C54 type TiSi₂ is initiated by the “self heating” thatis created by the high power density within portion 1310 of resistorlayer 210.

After the portion 1310 has been converted to C54 type TiSi₂ theresistance of resistor layer 210 drops further so that, for a givenvalue of current I₂, no more of the C49 type TiSi₂ will be converted. Asin the case of current I₁, the reaction for current I₂ is self limiting.

As the current through resistor layer 210 increases (e.g., from currentI₁ to current I₂), the area of high power density increases and more C49type TiSi₂ is converted to C54 type TiSi₂. This means that the effectiveresistance of resistor layer 210 decreases with increasing currentthrough resistor layer 210.

This means that it is possible to adjust the effective value ofresistance of resistor layer 210 by selecting the magnitude of thecurrent through resistor layer 210. That is, by selecting a first amountof current it is possible to produce a first value of resistance inresistor layer 210. By selecting a second larger amount of current it ispossible to produce a second smaller value of resistance in resistorlayer 210. The magnitude of the current through resistor layer 210 isselected to produce a desired value of resistance.

The current that is applied may pass through the resistor layer 210 ineither direction. That is, the current may be passed through thetriangularly shaped resistor layer 210 from either the narrow end or thewide end. It is the width of the triangularly shaped resistor layer 210(and not the direction of current flow) that determines which end willbe converted first.

FIG. 14 illustrates a flow chart 1400 showing the steps of a firstportion of an advantageous embodiment of the method of the presentinvention. The manufacture of resistor 200 of the present inventionbegins by providing a handle wafer 410. A silicon dioxide layer 420 isthen mounted on the handle wafer 410. A triangularly shaped layer ofpolysilicon 430 is then placed on the silicon dioxide layer 420 (step1410). Then a layer of titanium is applied over the triangularly shapedlayer of polysilicon 430 (step 1420).

Then a heat treatment is applied to heat the titanium layer to atemperature of approximately six hundred twenty degrees Centigrade (620°C.) to form C49 type TiSi₂ in polysilicon layer 430. The unconvertedtitanium is then removed (step 1430). Then a dielectric layer 610 isdeposited over the TiSi₂ layer 510 and portions of the silicon dioxidelayer 420 (step 1440). Then a mask and etch procedure is performed ondielectric layer 610 to etch a contact receptacle trench 620 at each endof the triangularly shaped layer of polysilicon 430 (step 1450).

Then a metal deposition procedure is performed to deposit metal 810 inthe contact receptacle trenches 620 to form input contact 220 and outputcontact 230 (step 1460). A metal etch procedure is then performed toetch away excess metal 810 and dielectric layer 610 (step 1470). Controlthen passes to step 1510 of FIG. 15.

FIG. 15 illustrates a flow chart 1500 showing the steps of a secondportion of an advantageous embodiment of the method of the presentinvention. Control passes to step 1510 from step 1470 of FIG. 14. A maskand metal deposition procedure is then performed to form input metalconnector 240 for input contact 220 and output metal connector 250 foroutput contact 230 (step 1510). These steps form the self heatingadjustable TiSi₂ resistor 200 of the present invention.

A current is then applied to the triangularly shaped resistor layer 210of resistor 200. The current enters resistor layer 210 from input metalconnector 240 and input contact 220. The current leaves resistor layer210 through output contact 230 and output metal connector 250 (step1520).

The current that passes through resistor layer 210 heats a highresistance portion of resistor layer 210 and converts a portion of theC49 type TiSi₂ to C54 type TiSi₂. The lower resistance of the C54 typeTiSi₂ decreases the effective resistance of the triangularly shapedresistor layer 210 (step 1530). A desired value of resistance for thetriangularly shaped resistor layer 210 may be selected by setting themagnitude of the current to a value that produces a desired value ofresistance.

Although the present invention has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present invention encompasssuch changes and modifications as fall within the scope of the appendedclaims.

1. A self heating adjustable titanium disilicon (TiSi₂) resistor, saidresistor comprising: a triangularly shaped layer of polysilicon placedon a layer of insulation material; a layer of titanium applied over saidtriangularly shaped layer of polysilicon; and a triangularly shapedlayer of C49 type titanium disilicon (TiSi₂) formed in said triangularlyshaped layer of polysilicon by heating said layer of titanium.
 2. Theself heating adjustable TiSi₂ resistor as set forth in claim 1 furthercomprising: an input contact coupled to a small end of said triangularlyshaped layer of polysilicon; an output contact coupled to a large end ofsaid triangularly shaped layer of polysilicon; an input metal connectorcoupled to said input contact; and an output metal connector coupled tosaid output contact.
 3. The self heating adjustable TiSi₂ resistor asset forth in claim 1 wherein a thickness of said layer of titanium isapproximately five hundred Angstroms (500 Å).
 4. The self heatingadjustable TiSi₂ resistor as set forth in claim 1 wherein saidtriangularly shaped layer of C49 type titanium disilicon (TiSi₂) isformed in said triangularly shaped layer of polysilicon by heating saidlayer of titanium to a temperature of approximately six hundred twentydegrees Centigrade.
 5. The self heating adjustable TiSi₂ resistor as setforth in claim 1 wherein said layer of C49 type TiSi₂ in saidtriangularly shaped layer of polysilicon does not include anyunconverted titanium.
 6. The self heating adjustable TiSi₂ resistor asset forth in claim 1 further comprising: a current applied to saidtriangularly shaped layer of C49 type TiSi₂ in said triangularly shapedlayer of polysilicon; and a portion of said triangularly shaped layer ofC49 type TiSi₂ converted to C54 type TiSi₂ having a lower resistancethan unconverted portions of said triangularly shaped layer of C49 typeTiSi₂.
 7. The self heating adjustable TiSi₂ resistor as set forth inclaim 6 further comprising: heat generated from said current in a highresistance portion of said triangularly shaped layer of C49 type TiSi₂;wherein said heat increases a temperature of said high resistanceportion of said triangularly shaped layer of C49 type TiSi₂ to atemperature that is at least approximately seven hundred degreesCentigrade.
 8. The self heating adjustable TiSi₂ resistor as set forthin claim 7 wherein said conversion of C49 type TiSi₂ to C54 type TiSi₂in said high resistance portion decreases a resistance of said highresistance portion to a level of resistance where no more C49 type TiSi₂is converted for said value of current.
 9. The self heating adjustableTiSi₂ resistor as set forth in claim 7 wherein a resistance of saidtriangularly shaped layer of C49 type TiSi₂ decreases when a magnitudeof said current increases.
 10. The self heating adjustable TiSi₂resistor as set forth in claim 1 further comprising: a current having aselected magnitude that flows through said triangularly shaped layer ofC49 type TiSi₂, wherein a resistance of said triangularly shaped layerof C49 type TiSi₂ is correlated with said magnitude of said current. 11.A self heating adjustable titanium disilicon resistor comprising: alayer of polysilicon having a narrower first end and a wider second end;and a layer of C49 type titanium disilicon formed in the layer ofpolysilicon, the layer of C49 type titanium disilicon comprising atleast a portion of a layer of titanium applied over the layer ofpolysilicon, at least the portion of the layer of titanium convertedinto the layer of C49 type titanium disilicon by heating the layer oftitanium.
 12. The self heating adjustable resistor of claim 11, wherein:the layer of polysilicon comprises a triangularly shaped layer ofpolysilicon; and the layer of C49 type titanium disilicon comprises atriangularly shaped layer of C49 type titanium disilicon.
 13. The selfheating adjustable resistor of claim 11, further comprising: an inputcontact coupled to the first end of the layer of polysilicon; and anoutput contact coupled to the second end of the layer of polysilicon.14. The self heating adjustable resistor of claim 13, furthercomprising: an input metal connector coupled to the input contact; andan output metal connector coupled to the output contact.
 15. The selfheating adjustable resistor of claim 11, further comprising: a portionof the layer of C49 type titanium disilicon converted to C54 typetitanium disilicon having a lower resistance than an unconverted portionof the layer of C49 type titanium disilicon.
 16. The self heatingadjustable resistor of claim 15, wherein the portion of the layer of C49type titanium disilicon converted to C54 type titanium disilicon isbased on a desired resistance of the self heating adjustable resistor.17. An integrated circuit comprising: a wafer; a layer of insulationmaterial over the wafer; and a self heating adjustable titaniumdisilicon resistor over the layer of insulation material, the selfheating adjustable titanium disilicon resistor comprising: a layer ofpolysilicon having a narrower first end and a wider second end; and alayer of C49 type titanium disilicon formed in the layer of polysilicon,the layer of C49 type titanium disilicon comprising at least a portionof a layer of titanium applied over the layer of polysilicon, at leastthe portion of the layer of titanium converted into the layer of C49type titanium disilicon by heating the layer of titanium.
 18. Theintegrated circuit of claim 17, wherein: the layer of polysiliconcomprises a triangularly shaped layer of polysilicon; and the layer ofC49 type titanium disilicon comprises a triangularly shaped layer of C49type titanium disilicon.
 19. The self heating adjustable resistor ofclaim 18, further comprising: an input metal connector coupled to theinput contact; and an output metal connector coupled to the outputcontact.
 20. The integrated circuit of claim 17, further comprising: aninput contact coupled to the first end of the layer of polysilicon; andan output contact coupled to the second end of the layer of polysilicon.